As the tobacco smoke filter designed to remove the tar component of tobacco smokes and yet offer a satisfactory smoking quality, a filter plug fabricated by molding a cellulose acetate fiber bundle with the aid of a plasticizer such as triacetin is in broad use. However, because the monofilaments in the bundle are partially fused to one another by the plasticizer, it takes a long time for this filter plug to disintegrate itself in the environment after being discarded after use and, thus, add to the pollution problem.
Meanwhile, a paper-based tobacco smoke filter made from a creped wood pulp sheet and a tobacco smoke filter comprising a regenerated cellulose fiber bundle are also known. Compared with the filter plug comprising a cellulose acetate tow (fiber bundle), these filters are somewhat greater in wet disintegratability so that the pollution problem can be mitigated to some extent. However, these filters are not only inferior in terms of smoking qualities but, compared with a cellulose acetate filter, significantly low in the selective elimination for phenols which is essential to any tobacco filter. Moreover, with a given pressure loss, the above filters are lower in hardness.
Japanese Patent Application Laid-open No. 96208/1977 (JP-A-52-96208) discloses a sheet comprising a cellulose acetate pulp prepared by a specified technology and short staples of a thermoplastic resin. Because this sheet is prepared by mix-webbing the pulp and short staples into a paper form and pressing the web under heating, it is large in tensile strength and elongation after immersion in water, high in water resistance, and extremely poor in disintegratability.
Japanese Patent Publication No. 38720/1975 (JP-B50-38720 discloses a tobacco smoke filter comprising a fibrous artifact with a surface area of not less than 3 m.sup.2 /g, which fibrous artifact is composed of fibrillated cellulose acetate microfibers with a diameter of 0.1 to 10 .mu.m. However, since this fibrous artifact has been highly fibrillated, the inter-filament adhesion is great enough to provide for high strength but is hardly disintegratable. Moreover, since the filter has a large surface area, the efficiency of elimination of harmful components from the tobacco smoke is high but as the aromatic component is also removed, the smoking quality is rather sacrificed.
Japanese Patent Application Laid-open No. 45468/1978 (JP-A-53-45468) discloses a filter material comprising a nonwoven fiber sheet containing 5 to 35% by weight of cellulose ester fibril with a diameter of 0.5 to 50 .mu.m and a surface area of not less than 5 m.sup.2 /g and 65 to 95% by weight of cellulose ester short staples. However, since the cellulose ester fibril has been highly fibrillated, the disintegratability of this filter material is also insufficient to alleviate the pollution problem and, moreover, the filter tends to detract from the smoking quality (aroma, taste and palatability) of tobacco.